Cancer therapy-induced ovarian failure is a significant public health problem with potentially 1% of population being affected over reproductive life span. Our overall goal is to understand and prevent the damage caused by such treatments. In the previous grant period we made significant discoveries which set the tone for the next grant period. We discovered that gonadotoxic chemotherapeutics result in primordial follicle death primarily by causing double strand (DSB) DNA breaks, and in response to this insult, oocytes mount an ATM- mediated DNA DSB repair response (Aging, 2011). This response may enable some primordial follicles to survive chemotherapy. Furthermore, we found that DNA DSB repair response is critical in the way oocytes mitigate genotoxic insult and aging, and that women who are deficient in DNA DSB repair, specifically BRCA1- mutation carriers, maybe prone to prematurely depleting their ovarian reserve (Science Translational Medicine, 2013). In addition, we showed that S1P, a naturally occurring ceramide death-pathway inhibitor, reduces chemotherapy-induced primordial follicle death in human ovarian xenografts (Human Reproduction 2014). Stemming from these revelations and the DNA DSB repair response being the unifying theme, our specific aims for the renewal application are: 1. To determine if BRCA-mutation carriers are more prone to chemotherapy-induced ovarian follicle loss because of their inherent deficiency of DNA DSB repair; 2. To reveal the mechanisms by which some primordial follicles are able to survive chemotherapy insult; 3. To understand how S1P protects human ovarian primordial follicle pool. To achieve these aims we will utilize clinical studies, single cel real time PCR as well as microarray strategies, in situ hybridization, gene interference, coupled with human ovarian xenografting and laser capture approaches. While the studies are primarily translational and will utilize human material, mouse models will also be used to strengthen the mechanistic work.